•  Injury of SLN (external branch) → hoarseness

•  Injury of RLN → unilateral paralysis → paralysis of ipsilateral vocal cord → hoarse voice; bilateral paralysis → stridor & respiratory distress

Airway Assessment

•  History

• Adverse events related to prior airway management

• Radiation/surgical history

• Burns/swelling/tumor/masses

• Obstructive sleep apnea (snoring)

• Temporomandibular joint dysfunction

• Dysphagia

• Problems with phonation

• C-spine disease (disk dz, osteoarthritis, rheumatoid arthritis, Down’s syndrome)

•  Physical examination

• Mallampati score (see also Chapter 1, Preoperative Assessment)

• Symmetry of mouth opening

• Loose/missing/cracked/implanted teeth

• Macroglossia (associated with difficult laryngoscopy)

• High-arched palate (associated with difficulty visualizing larynx)

• Mandible size

• Thyromental distance <3 fingerbreadths suggests poor laryngeal visualization

• Neck examination

• Prior surgeries/tracheostomy scars

• Abnormal masses (hematoma, abscess, goiter, tumor) or tracheal deviation

• Neck circumference & length

• Range of motion (flexion/extension/rotation)

Airway Devices

•  Oral and nasal airways

• Typically inserted secondary to loss of upper airway muscle tone in anesthetized patients → usually caused by tongue or epiglottis falling against posterior pharyngeal wall

• Length of nasal airway estimated by measuring from nares to meatus of ear

• Use caution with insertion in pts on anticoagulation or with basilar skull fractures

•  Mask airway

• Facilitates O₂ delivery (denitrogenation) as well as anesthetic gas using airtight seal

• Hold mask with left hand while right hand generates positive-pressure ventilation → (use <20 cm H₂O to avoid gastric inflation)

• One-handed technique

• Fit snugly around bridge of nose to below bottom lip

• Downward pressure with left thumb & index finger, middle, & ring finger; grasp the mandible while pinky finger is placed under angle of jaw to thrust anteriorly

• Two-handed technique

• Used in difficult ventilatory situations

• Bilateral thumbs hold mask down while fingertips displace jaw anteriorly

• Edentulous patients may be a challenge to ventilate (difficult to create a mask seal) → consider leaving dentures in place, oral airway, buccal cavity gauze packing

•  Difficult mask ventilation: Maneuvers to maintain airway patency

• Call for additional help (have someone else squeeze bag)

• Insert oral and or nasal airways

• Extend neck & rotate head

• Perform jaw thrust

•  Supraglottic airways (laryngeal mask airways)

• Insertion technique:

• Patient placed in sniffing position

• Deflated LMA cuff is lubricated & inserted blindly to hypopharynx

• Cuff is inflated to create a seal around entrance to larynx

• (Tip rests over upper esophageal sphincter, cuff upper border against base of tongue, sides lying over pyriform fossae)

• Indications

• Alternative to endotracheal intubation (not as a replacement) or mask ventilation

• Rescue device in expected/unexpected difficult airway

• Conduit for intubating stylet, flexible FOB, or small diameter ET

• Contraindications: Pharyngeal pathology, obstruction, high aspiration risk, low pulmonary compliance (need peak inspiratory pressures >20 cm H₂O), long surgeries

• Disadvantages: Do not protect the airway, can become dislodged

• Endotracheal tubes (ETTs)

• Used to deliver anesthetic gas directly to trachea & provide controlled ventilation

• Modified for a variety of specialized applications: Flexible, spiral-wound, wire-reinforced (armored), rubber, microlaryngeal, oral/nasal RAE (preformed), double-lumen tubes

• Airflow resistance depends on tube diameter, curvature, length

• All ETTs have an imprinted line that is opaque on radiographs

•  Rigid laryngoscopes: Used to examine larynx & facilitate tracheal intubation

• Macintosh blade (curved): Tip inserted into vallecula; use size 3 blade for most adults

• Miller blade (straight): Tip inserted beneath laryngeal surface of epiglottis; use size 2 blade for most adults

• Modified laryngoscopes: Wu, Bullard, & Glidescope for use in difficult airways

•  Flexible fiberoptic bronchoscopes

• Indications: Potentially difficult laryngoscopy/mask ventilation, unstable cervical spines, poor cervical range of motion, TMJ dysfunction, congenital/acquired upper airway anomalies

•  Light wand

• Malleable stylet with light emanating from distal tip, over which ETT is inserted

• Dim lights in OR & advanced wand blindly

• Glow in lateral neck → tip in piriform fossa

• Glow in the anterior neck → correctly positioned in trachea

• Glow diminishes significantly → tip likely in esophagus

•  Retrograde tracheal intubation

• Performed in awake & spontaneously ventilating pts

• Puncture cricothyroid membrane with 18-gauge needle

• Introduce guidewire & advanced cephalad (use 80 cm, 0.025 in. wire)

• Visualize wire with direct laryngoscopy & guide ETT through vocal cords

•  Airway bougie

• Solid or hollow, semimalleable stylets usually passed blindly into trachea

• ETT is threaded over bougie into trachea; can feel “clicking” as passes over tracheal rings

• May have internal lumen to allow for insufflation of O₂ & detection of CO₂

•  Video laryngoscopes (Glidescope^®, Storz^® V-Mac™, and McGrath^®)

• Usually a MAC style blade with a camera at the distal tip attached to a mobile video screen

• Assists with anterior airways, useful in obese pt; usually improves the view of the glottic opening; however, sometimes difficult to pass the ETT, unless a curved stylette is utilized

AIRWAY MANAGEMENT: OROTRACHEAL INTUBATION

•  Elevate height of bed to laryngoscopist’s xiphoid process

•  Place patient in sniffing position: Neck flexion, head extension; aligns oral, pharyngeal, & laryngeal axes to provide the straightest view from lips to glottis

•  Preoxygenate with 100% O₂

•  Induce anesthesia

•  Tape pt’s eyes shut to prevent corneal abrasions

•  Hold laryngoscope in left hand, scissoring mouth with right thumb & index finger

→ Insert laryngoscope in right side of mouth, sweeping tongue to left

→ Advance until glottis appears in view

→ Never use laryngoscope as a lever in a pivoting motion (instead lift “up and away”)

•   Using the right hand, pass the tip of the ETT through vocal cords under direct visualization

•  Inflate ETT cuff with least amount of air necessary to create seal during positive-pressure ventilation

•  Confirm correct placement of ETT with (1) Chest auscultation, (2) ETCO₂, (3) ETT condensation, (4) palpation of ETT cuff in sternal notch

Earliest manifestation of bronchial intubation is ↑ peak pressure (right mainstem bronchus common)

•  Rapid sequence intubation

• Indication: Pts at ↑ risk for aspiration (full stomach, pregnant, GERD, morbidly obese, bowel obstruction, delayed gastric emptying, pain, diabetic gastroparesis)

• Use rapid paralyzing agent: Succinylcholine (1–1.5 mg/kg) or rocuronium (0.6–1.2 mg/kg)

• Place cricoid pressure (Sellick maneuver) as pt is induced

• Protect from regurgitation of gastric contents to oropharynx

• Help visualize vocal cords during laryngoscopy

• Intubate pt once paralytic takes effect (30–60 sec); do not ventilate pt during this time

• Proper cricoid pressure should be performed with “BURP” technique:

• Displace larynx (B)ackward, (U)pward, (R)ight, with (P)ressure

•  “Modified” rapid sequence intubation

• A variation of the standard RSI technique in which a mask airway is established prior to administration of a paralytic agent

• May also include use of nondepolarizing agent (pts with ↑ K⁺)

Ehrenfeld, JM. et al. Modified rapid sequence induction and intubation: a survey of United States current practice. Anesth Analg. 2012 Jul;115(1):95–101.

AIRWAY MANAGEMENT: NASOTRACHEAL INTUBATION

•  Indications: Intraoral, facial/mandibular procedures

•  Contraindications: Basilar skull fractures, nasal fractures or polyps, underlying coagulopathies

•  Preparation: Anesthetize & vasoconstrict mucosa with lidocaine/phenylephrine mix or cocaine → select nares that pt can breathe through most easily

•  Lubricated ETT is advanced perpendicular to face below inferior turbinate via selected nares → direct bevel laterally away from turbinates

•  Advance ETT until able to visualize tip in oropharynx under direct laryngoscopy → use Magill forceps with right hand to advance/direct through vocal cords

AIRWAY MANAGEMENT: AWAKE FLEXIBLE FIBEROPTIC INTUBATION

•  Equipment: Ovassapian/Willliams/Luomanen airway, topical anesthetics, vasoconstrictors, antisialagogues, suction, fiberoptic scope with lubricated ETT

•  Indications: Cervical spine pathology, obesity, head & neck tumors, hx of a difficult airway

•  Premedication: Sedation (midazolam, fentanyl, dexmedetomidine, ketamine)

•  Technique:

• Take time to topicalize airway (key to success; see table below)

• Place special oral airway or grab tongue with gauze

• Keep fiberoptic scope in midline while advancing until epiglottis appears

• Advance scope beneath epiglottis using antero/retroflexion as needed

• Once vocal cords are visualized, advanced scope into trachea

• Stabilized scope while ETT is advanced off scope into trachea

→ If resistance is encountered, rotate ETT tube 90 degrees

• After insertion, visualize carina with scope to avoid endobronchial intubation

TRANSTRACHEAL PROCEDURES

•  Indications: Emergency tracheal access when an airway cannot be secured via nasal/oral route

•  Percutaneous transtracheal jet ventilation

• Simple & relatively safe means to sustain a patient during a critical situation

• Attach 12, 14, or 16-gauge IV catheter to 10 mL syringe partially filled with saline

• Advance needle through cricothyroid membrane with constant aspiration until you get air

• Advance angiocatheter, disconnect syringe, attach oxygen source

• High-pressure O₂ (25–30 psi), insufflation of 1–2 sec, 12/min with 16-gauge needle → will deliver approximately 400–700 mL

• Low-pressure O₂ (bag-valve-mask 6 psi, common gas outlet 20 psi)

•  Cricothyroidotomy

• Contraindications: Patients <6 yr/o (upper part of trachea not fully developed) → incision through cricothyroid membrane ↑ risk of subglottic stenosis

• Sterilize skin

• Identify cricothyroid membrane

• Transverse incision with #11 blade ≈1 cm on each side of midline

• Turn blade 90 degrees to create space to pass ETT

• Insert ETT caudally, inflate cuff, confirm breaths sounds

TECHNIQUES OF EXTUBATION

•  Extubation performed when pt either deeply anesthetized (stage 3) or awake (stage 1)

• Extubation during light anesthesia (stage 2) may → laryngospasm/airway compromise

•  Patient’s airway should be aggressively suctioned while on 100% O₂ prior to extubation

•  Prior to extubation, pt should be awake, following commands, neuromuscular blockade reversed

•  Untape ETT, deflate cuff, remove ETT while providing small amount of positive pressure

• Removes secretions at distal end of ETT

•  Place mask on pt with 100% O₂ while verifying spontaneous & adequate ventilation

•  Consider using 1.5 mg/kg of IV lidocaine 1–2 min before manipulation of airway & extubation (will blunt airway reflexes)

•  Deep extubation

• Indicated to prevent ↑ BP, ICP, IOP, or bronchospasm (in asthmatics)

• Contraindicated in pts at ↑ risk for aspiration or who may have a difficult airway

DIFFICULT AIRWAY ALGORITHM

Originally published in March 1993 & revised in 2003, the ASA Difficult Airway Algorithm (Figure 4-1) is designed to facilitate management of difficult airways & reduce adverse outcomes

Figure 4-1. ASA difficult airway algorithm. (Note: 30% of anesthesia-related deaths stem  from issues of airway management.)